Production of polymers from aromatic and the like compounds



United States Patent i PRODUCTION OF POLYMERS FROM AROMATIC AND THE LIKE COMPOUNDS Michael Mojzesz Szwarc, Syracuse, N. Y., and Alec Norman Roper and Herbert Max Emil Steiner, Manchester, England, assignors, by mesue assignments, to The M. W. Kellogg Company, Jersey City, N. J., a corporation of Delaware No Drawing. Application August 28, 1952,

'Serial No. 306,939

Claims priority, application Great Britain August 29, 1951 Claims. c1. 260-2 This invention relates to processes involving a pyrolysis step for the production of polymers from aromatic and the like compounds. I

' More particularly the invention relates to processes for the production of solid polymeric products in which the starting materials consist of aromatic compounds or aromatic heterocyclic compounds consisting of a single ring or of two condensed rings and having two methyl groups substituted in the para positions of one ring and in which the vapor of the starting material is pyrolyzed by being subjected to a temperature between 700 and 1000" C.

for not more than 10 seconds and the resulting vapors are cooled to a temperature at which a solid polymer is deposited. Such processes are described in British patent specifications Nos. 650,947 and 673,651 andin British patent application No. 20,346/ 51 on which are based the copending U. S. application-s, Serial Nos. 306,938 (now Patent No. 2,712,532) and 306,940, filed August 28,

Patent specification No. 650,947 discloses the use as one additional methyl substituent in the ring, for example, pseudocumene, durene, and isodurene.

U. S. Ser. No. 306,938 describes the production by the above process of copolymers from starting materials com-* prising a mixture of two or more polymethyl benzenes having from two to six methyl substituents in the ring with two of the, methyl substituents in the para positions, e. g. a mixture of para-xylene and pseudocumene.

In all these processes the vapor of the starting material is pyrolyzed at a temperature between 700 and 1000 C., and preferably between 800 and 950 'C., for not more than 10 seconds, and preferably for not more than one second, and the resulting vapors are cooled and condensed. Polymerization takes place spontaneously on condensation with the result that a solid polymer is deposited.

In these processes it is preferred to carry out the pyrolysis of the vapors of the starting material at low pressures and preferably at pressures in the region of 10 mms. Hg absolute or below. A convenient method of maintaining the partial pressure of the vapor to be pyrolyzed at a low figure is by dilution with an inert gas such as carbon dioxide or nitrogen and this is described in the British patents and U. S. applications referred to above.

:It has now been found surprisingly that steam, which is a relatively cheap and easily available material, forms 2,769,786 Patented Nov. 6, 1956 a satisfactory diluent and that the pyrolysis can be carried out with advantage in the presence of steam.

The invention thus consists in the processes for the production of the solid polymeric products referred to above, in which the pyrolysis of the vapor or mixture of vapors is carried out in the presence of steam.

The total pressure of the mixture of steam and the vapor of the organic starting material subjected to the pyrolysis temperature should be below atmospheric pressure and preferably between 100 and 200 mms. Hg absolute pressure. Preferably the partial pressure of the vapor of the starting material in the mixture is less than 10 mms. Hg absolute pressure.

The temperatures and contact times are not affected by the use of steam as the diluent and may suitably be within the range of 700 to1000 C. and not more than 10 seconds respectively. The preferred range of temperature is from 800 to 1000 C. and the preferred contact times from 1.0 to 0.02 second.

The process of the invention has been found particularly suitable for the production of solid polymeric products by the pyrolysis of the vapor or mixed vapors of polymethyl benzenes having from 2 to 6 methyl substituents in the nucleus with two of the methyl substituents in the parapositions, followed by cooling to a temperature at which a solid polymer is deposited. In this particular instance the pyrolysis is preferably carried out at a temperature of from 850 to 950 C. and with a contact time of from 1.0 to 0.02 second. Still more preferably the contact time does not exceed 0.5 second within this range of temperature.

The vapors resulting from the pyrolysis may suitably be cooled to between 50 and 0 C. in order to deposit the polymer.

superheated steam may be used with advantage to supply at least part of the heat required to raise the temperature of the starting material to the temperature at which the pyrolysis is to be carried out. For' example the vapor or vapors of the starting material may be preheated tobetween 500 and 600 C. and superheated steam may then be added to the vapor, to raise its temperature to the desired temperature of pyrolysis.

The polymeric products formed by the process of the invention are deposited in the form of a spongy mass which may be washed with benzene, ether or other suitable solvent'to remove condensed soluble material, and dried. The product is then in the form of flakes, which is an additional advantage.

Following are examples illustrative of the invention.

Example 1 A mixture of steam and p-xylene vapor in the molar ratio of 11:1, the total vapor pressure of the steam and the p-xylene being approximately 100 mms. Hg absolute pressure, was passed through a silica tube heated to 900 C. at such a rate that the vapor was subjected to this temperature for approximately 0.08 second. The vapor leaving the tube was passed into a trap in which it was cooled to room temperature with the result that a polymeric product was deposited as a spongy mass. This 7 mass was washed with acetone to remove soluble material and dried. The dry polymer was recovered in the form of flakes.

Example 2 A mixture of steam and the vapor of 2 chloro-p-xylene in the molar ratio of :1, the total vapor pressure of the steam and vapor of 2 chloro-p-xylene being about mms. Hg absolute pressure was passed through a silica tube heated to about 885 C. at such a rate that the vapor was subjected to this temperature for 0.09 second. The pyrolyzed vapors were cooled to room temperature. A

3 spongy mass was deposited which was washed with benzene and dried to recover the polymeric product in the form of flakes. f

Examples 3 to 5 A similar procedure to that described in Example'l was followed with 2,5-dimethyl pyrazine, pseudocumene and a mixture of pseudocumene and p-xylene as starting materials under the conditions set out in the following table. In each case the polymeric product was recovered" The following two examples illustrate the use of superheated steam to raise the temperature of preheated p-xylene to the temperature of pyrolysis.

Example 6 Steam at 1050 C. and the vapor of p-xylene preheated to 600 C. in the molar ratio of 19:1 were passed together through a heat-insulated reaction tube, the resulting temperature of the mixture in the tube being about 950 C. and the pressure being about 100 mms. Hg absolute pressure. The rate of passage through the tube was such that the residence time within the tube was 0.05 second. The vapors leaving the tube were cooled to room temperature. A spongy mass was deposited which was washed with benzene and dried to recover the polymeric product in the form of flakes.

Example 7 Steam at 1000 C. and the vapor of p-xylene at 600 C. in the molar ratio of 14:1 were passed together through a heat-insulated reaction tube, the resulting temperature of the mixture in the tube being about 900 C. and the total vapor pressure being about 100 mms. Hg absolute pressure. The rate of passage through the tube was such that the mixture was subjected to the temperature of about 900 C. for 0.20 second. The vapors leaving the tube were cooled to room temperature. Aspongy mass was deposited which was washed with ether and dried to recover the polymeric product in the form of flakes.

We claim:

1. A process as claimed in claim 8 in which the vapor of p-xylene is pyrolyzed.

2. A process as claimed in claim 8 in which the vapor of pseudocumene is pyrolyzed.

3. A process as claimed in claim 7 in which, the mixed vapors of p-xylene and pseudocumene are pyrolyzed.

4. In the production of polymeric products in the form of flakes, the process which comprises pyrolzing the vapors of at least one aromatic compound; selected from the class consisting of para-xylene, para-xylenes substituted in the nuceus with from 1 to 2 atoms of a normally gaseous halogen and para-xylenes substituted in the nucleus with at least one methyl group in addition to the para methyl groups; by heating said vapors to temperatures within the range of from about 700 to 1000 C. for a time ranging from about 1 second to 0.02 second and under a total pressure not exceeding 200 mms. Hg absolute, steam in substantial proportions being mixed with said vapors before the pyrolysis, cooling the pyrolyzed vapors to precipitate the resulting polymer, washing and drying to recover the polymer in flake form.

5. The process of claim 4 in which the steam is mixed with the aromatic vapors in molecular proportions ranging from about 10:1 to 100:1. I

6. The process of claim 4 in which the steam is superheated before being mixed with the aromatic vapors to temperatures sufiiciently high to raise the temperature of the mixture within the range of from 700 to 1000 C.

7. In the production of polymeric products in the form of flakes, the process which comprises pyrolyzing the vapors of a mixture of at least two polymethyl benzenes, having from 2 to 6 methyl substituents in the nucleus with two in para position with respect to each other, by heating said vapors in admixture with steam in molecular proportions ranging from about 10 to 100 moles of steam to 1 mole of the polymethyl benzene vapors to a temperature of from about 850 to 950 C. for a time ranging from about 0.5 to 0.02 second and under a total pressure of steam and mixed polymethyl benzene vapors not exceeding 200 mm. mercury absolute, cooling the pyrolyzed vapors to a temperature of from about 50 to 0 C. to precipitate the resulting polymer, washing and drying to recover the polymer in flake form.

8. In the production of polymeric products in the form of flakes, the process which comprises pyrolyzing the vapors of a polymethyl benzene, having from 2 to 6 methyl substituents in the nucleus with two in para position with respect to each other, by heating said vapors in admixture with steam in molecular proportions ranging from about 10 to 100 moles of steam to 1 mole of the polymethyl benzene vapors to a temperature of from about 850 to 950 C. for a time ranging from about 0.5 to 0.02 second and under a total pressure of steam and polymethyl benzene vapors not exceeding 200 mm. mercury absolute, cooling the pyrolyzed vapors to a temperature of from about 50 to 0 C. to precipitate the resulting polymer, washing and drying to recover the polymer in flake form.

9. In the production of polymeric products in the form of flakes, the process which comprises pyrolyzing the vapors of a polymethyl benzene having two methyl substituents in the para positions and at least one additional methyl substituent in the ring, by heating said vapors in admixture with steam in molecular proportions ranging from about 10 to 100 moles of steam to 1 mole of the polymethyl benzene vapors to a temperature of from about 700 to 1000 C. for a time ranging from about 1 second to 0.02 second and under a total pressure of steam and polymethyl benzene vapors not exceeding 200 mm. mercury absolute, cooling the pyrolyzed vapors to a temperature of from about 50 to 0 C. to precipitate the resulting polymer, washing and drying to recover the polymer in flake form.

' lected from the class consisting of chlorine and fluorine,

by heating said vapors in admixture with steam in molecular proportions ranging from about 10 to 100 moles of steam to 1 mole of the substituted para-xylene vapors to a temperature of about 700 to 1000 C. for a time ranging from about 1 second to 0.02 second and under a total pressure of steam and substituted para-xylene vapors not exceeding 200 mm. mercury absolute, cooling the pyrolyzed vapors-to a temperature of from about 50 to 0 C. to precipitate the resulting polymer, washing and drying to recover the polymer in flake form.

References Cited in the file of this patent UNITED STATES PATENTS 1,875,317 Carothers Sept. 6, 1932 2,143,509 Conover Jan. 10, 1939 2,524,318 Kharasch Oct. 3, 1950 FOREIGN PATENTS 650,947 Great Britain Mar. '7, 1951 

9. IN THE PRODUCTION OF POLYMERIC PRODUCTS IN THE FORM OF FLAKES, THE PROCESS WHICH COMPRISES PYROLYZING THE VAPORS OF A POLYMETHYL BENZENE HAVING TWO METHYL SUBSTITUENTS IN THE PARA POSITIONS AND AT LEAST ONE ADDITIONAL METAL SUBSTITUENT IN THE RING, BY HEATING SAID VAPORS IN ADMIXTURE WITH STEAM IN MOLECULAR PROPORTIONS RANGING FROM ABOUT 10 TO 100 MOLES OF STEAM TO 1 MOLE OF THE POLYMETHYL BENZENE VAPORS TO A TEMPERATURE OF FROM ABOUT 700* TO 100* C. FOR A TIME RANGING FROM ABOUT 1 SECOND TO 0.02 SECOND AND UNDER A TOTAL PRESSURE OF STEAM AND POLYMETHYL BENZENE VAPORS NOT EXCEEDING 200 MM. MERCURY ABSOLUTE, COOLING THE PYROLYZED VAPORS TO A TEMPERATURE OF FROM ABOUT 50* TO 0* C. TO PRECIPITATE THE RESULTING POLYMER, WASHING AND DRYING TO RECOVER THE POLYMER IN FLAKE FORM. 